In mammals, dizziness is a symptom that causes a disruption in determining the body’s location in space and physical stability. Dizziness is often classified as vertigo, disequilibrium, and presynchopy—defined as being lightheaded or faint. Conditions that cause dizziness are often wide and varied because there are many body systems that are responsible for balance, such as the inner ear, the central nervous system, and the muscular system. The most common form of dizziness is vertigo; it causes more than 50 percent of all clinical cases of dizziness (Hornibrook, 2011). Vertigo is a disease process that is defined as a type of dizziness that produces the sensation of rotational or spinning movement despite the body remaining still. In addition to the sensation of movement, affected individuals often suffer from nausea and balance issues that make it difficult to stand or walk straight. Vertigo can be classified into two categories: peripheral or central. Peripheral vertigo is the result of vestibular system dysfunction within the semicircular canals or the otolith organs. Central vertigo generally causes balance issues and not the perception of movement, as in peripheral vertigo. Causes of central vertigo are often stroke, brain tumor, hemorrhage, or epilepsy.
Dizziness and vertigo are commonly reported in the general population; it can be a primary disease or symptom that is secondary to another disorder. Individuals of all age groups can show signs and symptoms of vertigo. Individuals experiencing vertigo can have acute attacks lasting a few seconds to a few minutes, or they can have chronic symptoms with the experience lasting for hours and recurring over an extended time frame. Vertigo is caused either by a dysfunction in the peripheral nervous system or by disorders of the central nervous system. Peripheral vertigo originates in the vestibular system and common causes of peripheral vertigo are benign paroxysmal positional vertigo (BPPV), vestibular neuritis, and Meniere’s disease. Central vertigo originates from issues within the central nervous system including brain hemorrhage, vestibular nerve lesions, and multiple sclerosis.
BPPV is the most common type of peripheral vertigo and is accompanied by the sudden sensation of spinning. The episode of dizziness associated with BPPV ranges from mild episodic cases to prolonged intense dizziness. In a normal functioning vestibular system, small calcium carbonate particles called otoconia are located within the otolith organs (saccule and utricle), which are part of the vestibular labyrinth of the inner ear. In BPPV, the otoconia are inappropriately displaced into the semicircular canals of the vestibular labyrinth within the inner ear. Normally, these stones are attached to a gelatinous membrane within the utricle and saccule. When the otoconia are free to move within the semicircular canal, a head tilt allows the stones to shift the endolymph, resulting in neural impulses. This creates the false sense of motion that causes the dizziness experienced in BPPV. Any head motion that would normally stimulate the semicircular canals such as head tilting, turning suddenly, looking up or down, and rolling over in bed can trigger BPPV. Unilateral BPPV is the most common form of this disease; however, BPPV can be bilateral and affect the vestibular organs on both sides of the head.
Common signs and symptoms of BPPV include (1) dizziness—the sensation that the surroundings are moving although the person is still, (2) lightheadedness, (3) loss of balance, (4) blurred vision, (5) nystagmus, (6) nausea, and (7) vomiting. In general, these signs and symptoms are recurrent and short in duration. Nystagmus is a common symptom of vertigo that is triggered by the vestibulo-ocular reflex (VOR). The VOR reflex loop connects the movements of the eye to the motions of the head sensed by the vestibular system. When an individual is dizzy, the VOR tries to compensate for the perceived movement with a rapid side-to-side eye “twitching” movement.
Specific causes of BPPV are generally linked to head injuries such as concussions or even migraine headaches. Other causes of BPPV include damage to the inner ear by some unknown cause or by damage to the inner ear during ear surgery. Doctors may use a diagnostic test called electronystamography (ENG) or videonystagmography (VNG) to determine if a patient has the nystagmus associated with inner ear BPPV. These tests measure the rapid eye movements associated with BPPV while the patient moves his or her head in different directions. However, to determine central nervous system vertigo, health care providers may use magnetic resonance imaging (MRI). The main treatment of BPPV is a simple technique called the canalith-repositioning procedure, which must be performed by a health care provider or a trained professional. This practice uses several slow, purposeful head movements, which force the loose otoconia to move back to the utricle and saccule and become reembedded into the gelatinous membrane. In general, the patient will need to have one or two treatments for this procedure to be effective. In rare cases, if the canalith-repositioning procedure is not successful, then surgical interventions must be used to alleviate BPPV.
See also: Central Nervous System; Peripheral Nervous System; Vestibular System
Hornibrook, Jeremy. (2011). Benign paroxysmal positional vertigo (BPPV): History, pathophysiology, office treatment and future directions. International Journal of Otolaryngology, Article ID 835671. http://dx.doi.org/10.1155/2011/835671.
Vestibular Disorder Association. (2013). Labyrinthitis and vestibular neuritis. Retrieved from http://vestibular.org/labyrinthitis-and-vestibular-neuritis